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Django

Notes:

  • To install Django in system run

    pip3 install django

  • Every time you start some project, create a new folder and

    • run command
    django-admin startproject project-name
    • This will create a folder with the specified project-name containing all required files

  • to start django server , run command

    python3 manage.py runserver

  • the django framework works on

    localhost:8000

Starting with a webapp

Webapp refers to a part of your website. In Django the webiste is divide into various applications with each application having its own work.

  • to create a webapp, run command

    python3 manage.py startapp app-name

  • the webpages are routed as functions inside views.py
    Example

    from django.http import HttpResponse

def index(request):
    return HttpResponse("<h1>Text-Message</h1>")
    # HttpResponse is used like a print function to print something on web page
    # request is used to get the webpage

  • Every app in a project contains a file called urls.py which contains all the links related to that specific project

  • in urls.py insert code as

    from django.urls import path
from . import views

urlpatterns = [
    path("",views.index,name="index"),
    path("/app1",views.func2,name="func2")
]
# "" empty string denotes localhost:8000

Using Templates

MADE SURE ALL FILES ARE PROVIDED EXECUTABLE PERMISSIONS , TO BE PRECISE 755

  • In Django, to use html pages, templates are used
  • Inside your webapp, create a new folder called templates and inside it make another folder with webapp name
$ mkdir -p templates/web-app
  • Save all the html files inside this folder
  • Then open, settings.py file from main project folder
  • add entry
TEMPLATES = [
    {
        'DIRS': ["app-name/templates",],
    }
]

  • To open some html webpage(template) ,In views.py file write

    from django.shortcuts import render

def index(request):
    return render(request,"app-name/page-name-stored-in-templates-dir.html")
# render works to route the url to indicated web-page

  • By Default, Django search for the folder specified in the settings.py file for templates

  • To route to a different web-page using anchor-tag,the syntax is

<a href="% url 'name-of-url-from-urls.py' %">text-to-work-as-link</a>
<!-- {% something %} is a format of 'jinja' language -->
  • For similar structured web-pages,instead of repeating the html code
    1. create a base.html file with the html structure code
    <!DOCTYPE html>
<html>
    <head>
        <title>{% block title %}{% endblock %}</title>
    </head>
    <body>
        {% block body %}
        {% endblock %}
    </body>
</html>
    1. For all other files, the code will be similar to
    {% extends "path-of-base.html" %}

{% block title %}
    Title-of-your-page
{% endblock %}

{% block body %}
    <h1> this is my body content </h1>
{% endblock %}

Using CSS,JS,BootStrap

MADE SURE ALL FILES ARE PROVIDED EXECUTABLE PERMISSIONS , TO BE PRECISE 755

  • All CSS,JS and BootStrap.. these are static files which have no need to be changes thus In Django,these are known as static files
  • All static files are stored inside the app in a directory named static same as templates.
  • So for all img,css,js and bootstrap,create two directories inside web-app folder
mkdir -p static/web-app/
  • In settings.py file of main folder add a new entry in the list of INSTALLED_APPS
INSTALLED_APPS = [
    'web-app.apps.webappConfig',
]
  • Finally inside your html file, do the following changes
    1. code should be initiated with following jinja code
    {% load static %}
    1. Replace the html src tags syntax in this way
    <img src="folder1/img/img1.jpeg"> to 
<img src="{% static 'web-app/img/img1.jpeg' %}">

<!-- Similarly -->
  <link href="lib/owlcarousel/assets/owl.carousel.min.css" rel="stylesheet">
                        to

<link href="{% static 'QuizMania/lib/owlcarousel/assets/owl.carousel.min.css' %}" rel="stylesheet">
  • {% static %} -> it tells to load the nearest static folder inside html code
  • {% static 'path' %} -> is used to define the path inside of static folder for the specific file

Routing From One Page to another (anchor)

  • Onclick ~ button function(using js)
    1. to make a certain line of text clickable, run code in this similar context 
      <div class="col-md-6 col-lg-3">
  <div class="feature-block">
  <img src="{% static 'QuizMania/img/docker.svg' %}" alt="img" class="img-fluid">
    <h4>Docker</h4>
    <p onclick="Docker()">Docker is a set of coupled software-as-a-service and platform-as-a-service products that use operating-system-level virtualization to develop and deliver software in packages called containers. The software that hosts the containers is called Docker Engine. </p>
  </div>
</div>
      <script>
    function Docker(){
        location.replace("{% url 'test' %}")
    }
</script>
    2. onclick="function-name()" is used to point to the js code in script tag.
    3. location.replace is used to replace the context of current page with another with replacing chance to go back to previous page
    4. {% url 'name-of-url-in-urls.py' %} -> used to point to the different url to send on clicking the text
  • After the above code , in html file, add the following lines in urls.py file pf web-app 
    from django.urls import path
from . import views
urlpatterns = [
    path("",views.index),
    path("any-text-to-show-after-/",views.function-name-to-change-page,name="name-for-this-url"),
    ]
  • Make a new function in views.py that will do the work to render from current page to another 
    def function-name(request):
return render(request,'web-app/page-to-load.html')
  • OR instead of above code,just do the following
    1. in the input tag, write
    <p onclick="window.location.href='http://localhost/2'" >any-text</p>
    1. the text will move to different url on click

Using Loops in Templates

  • for loop can be implied in a template easily using jinja format
  • remember that , jinja by default thinks of range(value) as string only
  • its syntax is like
<ul>
{% for test in '123' %}
    <li>hello</li>
{% endfor %}
</ul>
  • the above code will print hello as list item 3 times
  • the variable test can be accessed as {{test}}

Database

MADE SURE ALL FILES ARE PROVIDED EXECUTABLE PERMISSIONS , TO BE PRECISE 755

  • To create a superuser to access all the tables inside a database,run command 
     python manage.py createsuperuser
  • The tables and databases are creates in models.py file
  • context keyword is used to create a dictionary inside a function of views.py which can be accessed as a variable Example
from django.http import HttpResponse
from django.shortcuts import render

def index(request):
    context = {
        "key-name": database-class-name.objects.all()
    }
    return render(request,"html-page-to-take-the-data-to-from-database",context)

Create New Table

  • To create any kind of table ,just
    1. open models.py
    2. write in the following pattern
    from django.db import models

class table-name(models.Model):
    column1-name = models.CharField(max_length=45)
    column2-name = models.IntegerField(max_length=10)

    # the way to represent the data when called
    def __str__(self):
        return f"{self.column1-name} its just a string {self.column2-name} "
    1. to commit changes in database , run command it will create a table and output a id
    python manage.py makemigrations
    1. To check the actual SQL query would have needed to do the upper task , run command
    python manage.py sqlmigrate project-name table-id
    1. To finally apply all the changes , run command
    python manage.py migrate

Table Relationships

  • To define relationships between different tables, django supports various formats such as :
    1. ForeignKey(table-name,on_delete=models.CASCADE,related_name="")
    2. ManyToMany(table-name,on_delete=models.CASCADE,related_name="")
  • on_delete function: it is used to delete an entry automatically if its deleted from linked table
  • related_name: it is used to refer the column and access its content with .

Admin-Database Configuration

  • file admin.py contains list of all the tables made inside a project
  • the file looks like, 
    from django.contrib import admin
from .models import Table-name1, Table-name2
# register models name
admin.site.register(Table-name1)
admin.site.register(Table-name2)

Data Extraction from forms

  • its very simple to extract data from some page that is by: 
    variable-name = request.POST['name-of-input-field']
  • To redirect user to any other page 
    from django.http import HttpResponseRedirect
from django.urls import reverse
def redirect_function(request):
    return HttpResponseRedirect(reverse("name-of-url",args=None/if-any))
  • to show 404 error page 
    from django.http import Http404
try:
    # some statements
except:
    raise Http404("Statement to show as error")
  • while making forms always make sure to add {% csrf_token %} tag inside the form
  • csrf_token : By default, for security reasons , django doesn't support submission of forms and thus requires this token to know that actually our web application is submitting this form

Users Authentication

  • Create a new app called authentication

Urls.py

  • it contains 3 urls:
    1. index page
    2. login page
    3. logout page

Views.py

  • for session authentication of user at index page 
    from django.shortcuts import render

def index(request):
    if not request.user.authenticated:
        return render(request,"users/login.html",{"message":None})
    context = {
        "user":request.user
    }
    return render(request,"users/user.html",context)
  • for login authentication, if users entered credentials are right or not, 
    from django.contrib.auth import authenticate,login
from django.http import HttpResponseRedirect
from django.shortcuts import render

def login_check(request):
    username = request.POST["username-field-name"]
    password = request.POST["password-field-name"]
    user = authenticate(request,username=username,password=password)
    if user is not None:
        login(request,user) # it is predefined django function to set the cookies
        return HttpResponseRedirect(reverse("index-page-name-in-urls.py"))
    else:
        return render(request,"users/login.html",{"message":'Invalid Credentials'})
  • for logout , to make sure session is removed for current user, the following code is useful 
    from django.contrib.auth import logout
from django.shortcuts import render

def logout_check(request):
    logout(request,user)
    return render(request,"users/login.html",{"message":"Logged Out Successfully"})

To add Users in your system Database

  • Ways to be able to add users

    1. way is through Django interface shell manually
    from django.contrib.auth.models import User

user = User.objects.create_user("name-of-user","email-of-user","password-of-user")

user.save()
user.commit()
    1. we can create a registeration page and in backend run the program to insert data inside the database

  • User object has various other field , that can be used to store data inside user dataabse,such as:

    1. first_name
    2. last_name
    3. administrator or not
    4. username etc

  • To user modification properties of User model,just follow the similar syntax

    from django.contrib.auth.models import User

user = User.objects.create_user("name","email","pass")
user.first_name = "set-any-first-name"
user.save()
user.save()

HTML

Attributes

ID

  • it can be used to make a particular id for a specific tag such it can be referred to later easily
    • example 
      <h1 id="section1">Hello</h1>
<h2 id="chutiya" > World</h2>
< a href="#section1">link</a>
  • on clicking link, it will scroll the page to h1 tag